Response characteristics of nasal trigeminal nociceptors in Gallus domesticus

Although the chemoreceptive properties of the nasal trigeminal system are well known, the physiological characteristics of nasal nociceptors responding to both mechanical and chemical stimulation have not been well described. In this study, the activity of single nasal trigeminal units recorded from microdissected twigs of the ethmoidal nerve of anaesthetized hens (Gallus domesticus) was investigated. Using a mechanical search stimulus, 20 slowly and 22 rapidly adapting nasal mechanoreceptors were identified, exhibiting mean thresholds of 2.96 g. Twelve slowly adapting units also exhibited chemical sensitivity when exposed to ammonia gas. These had mean response thresholds of 0.232% vapour saturation and exhibited variable stimulus-response profiles. This is the first study to quantify the responses of polymodal nasal nociceptors to a noxious airborne chemical in any species.